A MgC12/THF/TiC14bimetalliccomplexcatalyst was prepared by reacting magnesium chloride with titanium tetrachloride in tetrahydrofuran(THF). During the temperatureprogrammeddecomposition(TPD) of the bimetalliccomplex, THF and 1,4 dichlorobutane were identified by Mass spectroscopy(MS). THF decoordinated from Ti species reacted with adjacent Cl, resulting in the formation of 1, 4–dichlorobutane. When the MgC12/THF/TiC14bimetalliccatalyst (Mg/Ti=5.2) was heated below 108 °C, the catalytic activity of polymerization increased, while it decreased above 140 °C. In ethylene-1–hexene copolymerization, the lowest catalytic activity was obtained at the molar ratio of hexene to ethylene in monomer feed(CH/CE), 1.14 or 2.22. The comonomer distribution of copolymer prepared with thermally pretreated catalyst was more homogeneous than that of copolymer prepared without thermal treatment.